1. Field of the Invention
The present invention generally relates to medical devices used to expand tubular membranes. More particularly, the present invention is designed to mitigate prostatic hypertrophy by the use of a semi-permanent stent.
2. Background Information
Many vessels in the human body have a tendency to become obstructed or constricted after a period of years, causing severe side affects. For example, arteriosclerosis, or hardening of the arteries, is a result of a buildup of placque on the inner walls of the coronary arteries, leading to reduced blood flow and oxygen intake by the cardiac muscle. The present invention is directed to a device designed to mitigate or alleviate such constriction in any one of several ducts and vessels of the body. Actually, the present invention was originally developed in order to diminish the effects of prostatic hypertrophy.
The prostate gland is located next to the inner wall of the rectum, around the urethra and directly below the bladder. If the prostate becomes swollen, due to infection or some disease, it will crowd the urethra and cause discomfort. Typically, as a man nears fifty years of age, the gland begins to grow in size, apparently due to hormonal changes. This is enlargement is known as benign prostatic hypertrophy, or BPH. Sixty percent of men over 60 have BPH, and nearly 95% of men over 80 suffer from this condition. The enlargement of the glandular tissue within the prostatic capsule can cause not only minor trouble, such as nocturia (waking up at night to urinate) or overflow incontinence, but can further lead to uremia (excess urea in the blood), renal failure, and even death.
BPH is not a recent disease of the twentieth century, and some treatments have been known for literally thousands of years. The ancient Egyptians knew of prostatic enlargement, and inserted reeds, or copper or silver tubes through the penis and urethra to widen the urinary passage in the gland. Benjamin Franklin has been credited with inventing a urethral catheter for use by his brother, a victim of prostatic obstruction.
Catheters are used today to ease acute retention of urine brought about by BPH. The most common of these is the Foley catheter developed by Dr. Frederick Foley. The Foley catheter is, however, at best a temporary measure providing only transitory relief. Prostatic massage can also provide temporary relief in cases where BPH is accompanied by congestion of the thirty to fifty tubes or saclike ducts within the prostate gland, but this usually only postpones surgery. For permanent relief of the condition, some form of surgery is generally required. Administration of female hormones will diminish the disorder, but the side effects of this treatment make it most undesirable.
Presently, there are four different surgical procedures available to remove all or part of the prostate gland. The first of these is transurethral resection (TUR). In this procedure, a stiff, hollow sheath is first inserted into the penile urethra, and then a fiber optic instrument similar to a cystoscope, known as a resectoscope, it passed through the sheath to the prostate area. A looped piece of wire carrying an electrical current is moved back and forth, cutting away excess prostatic tissue. An indwelling drainage catheter, such as those shown in U.S Pat. No. 3,394,705 issued to D. Abramson, and U.S. Pat. No. 4,571,241 issued to T. Christopher, is left in the urethra and bladder for twenty-four hours after the operation.
The problem with TUR's is that, if the prostate has grown to a relatively large size, the patient will probably need another surgical procedure. This is highly undesirable since most men are already fairly old when they have a TUR, and will likely be less healthy when the procedure is repeated. Where a large amount of the prostate is removed, two other techniques may be used: suprapubic and retropubic prostatectomies.
In a suprapubic prostatectomy, an incision is made between the navel and the pubic bone. The incision is typically four to six inches long. An incision is further made in the bladder itself, and the prostate gland is then removed. In the retropubic prostatectomy, the same initial incision is made, but the bladder is left undisturbed. Rather, the intestines are pushed away from the bladder, and the fibrous capsule surrounding the prostate gland is severed. All or some of the gland is then removed.
The fourth procedure is known as a perineal prostatectomy. In this technique, an incision is made through the perineum, between the anus and scrotum. This provides a more direct route to the gland, but it can have several undesirable consequences, including impotency due to severed nerves. All three of the prostatectomies are basically unappealing as they introduce all of the complications of open surgery.
One final method of cryosurgery has been recently attempted with uncertain results. In that method, a probe containing liquid nitrogen is inserted into the urethra, shrinking away swollen tissue. Physicians are expectedly cautious in discussing the merits of this procedure.
Along another vein, physicians have created several different catheters designed to dilate stenoses or occlusions in a body passageway. For example, U.S. Pat. No. 4,493,711 issued to Chin et al. is directed to a extrusion catheter providing means for placement of a soft tube through the lumen of an occluded artery or vein. Several dilation catheters were designed for coronary angioplasty; these include: U.S. Pat. No. 4,413,989 issued to Schjeldahl et al.; U.S. Pat. No. 4,315,512 issued to Fogarty; and U.S. Pat. No. 4,195,637 issued to Gruntzig et al. It would be possible to utilize such catheters in BPH patients, but the catheters only temporarily expand the prostatic urethra, and the enlarged prostate will nearly immediately return to its collapsed position.
It would, therefore, be desirable and advantageous to devise a dilation stent which could be permanently placed in the prostatic urethra to relieve benign prostatic hypertrophy. The inventor knows of no such stent which, once in place, could expand to enlarge the urethra. Such a stent could also be used for other ducts and vessels in the body. There is one variable diameter catheter, disclosed in U.S. Pat. No. 4,601,713 issued to C Fuqua, that may be longitudinally folded for insertion into the urethra and then unfolded after insertion for transporting a fluid therein, but that catheter is also a temporary device in which one end of the catheter exits the body for access to an external source of fluids. Also, no catheter or stent can be placed in a body orifice in a permanent fashion, and yet be later removed should complications arise.